Loss of tuning - ish

[Woodentop]

I turned our bedroom unit on for the first time in a while a week or two ago and it would not find a station. I went into manual tune and selected channel 47 (Emley Moor BBC mux) and it showed 61% signal and 100% quality. When I set the box to do a retune on channel 47 it cannot not find any stations - and it is the same on all the other muxes. Passthrough to the TV works perfectly. I set it to do autotune and again it couldn't find anything.
I went into the hidden menu to look at signal information and it just shows 'NONE' on both tuners.
I also have a YouView Hummy and that connected to the same antenna and HDMI connections shows the BBC mux as 53% signal and 100% quality and it will tune. OK, as a YV box doesn't have manual tune I had to set it going and it found 171 stations which is about right.
Downstairs I have another unit fed by a different cable from the same aerial and distribution amp. It too shows chan 47 as 56% signal and 100% quality and tunes perfectly.
Anyone any ideas? If it was showing signal and quality before I tried a retune it suggests the tuner is OK, so what else could it be?

 

[Black Hole]

I find it particularly odd that (from my understanding of your post) the signal detection section of the menu shows signal, but the individual tuner test (via hidden service menu) shows none.

Our HDRs are getting old, there are going to be weird failures. So far as I can see: if a factory reset doesn't fix it, a system flush doesn't fix it, and re-installing the firmware doesn't fix it, there's nothing more to be done.

 

[Woodentop]

For the record I bit the bullet and did a Factory Reset and indeed it cures the problem.

Many thanks to all replies.